The present invention relates to a method of producing frozen minced fish meat (referred to as "frozen surimi").
Conventionally, frozen surimi has been produced by the process in which minced fish meat obtained from a fish meat, such as pollack, is subjected to two or more washes with fresh water, with the addition of a small amount of common salt to the fresh water used at the last wash step, removal of skin by a refiner where necessary, dehydrating by a screw-press, and then mixing with the addition of sugars or sugar alcohols, polyphosphates, etc. Finally the product is packed and stored under refrigeration at minus 20.degree. C.-30.degree. C. until delivery.
Recently, however, the human intake of phosphates, such as polyphosphates which are used as additives in foods, has a tendency to increase, because of increased public consumption of processed foods. This tendency has been raising an apprehension concerning public health, because excessive intake of phosphates will lead to calcium deficiency due to an imbalance between calcium and phosphate in human bodies. It is desirable, therefore, to reduce phosphate content in foods, including frozen surimi. Frozen surimi meat containing no phosphate is now a goal of the fish processing industry.
In connection with this, a method for the complete elimination of phosphates, such as polyphosphates, from frozen surimi was proposed under a Japanese Patent (Toku Ko Sho No. 47-23385). The method disclosed consists of adjusting the pH of minced fish meat (raw surimi) that has been mixed with additives to a value within the range of pH 7.5-9.0 before it is put into storage under refrigeration, thereby preserving unimpaired the quality of the protein for long periods of time.
The above-stated method involves disadvantages however. Surimi preserved under refrigeration at such a high pH value tends to undergo premature "suwari" (increase of elasticity) when it is thawed. Though suwari is a necessary property for surimi based products, premature suwari (before production of the suwari based products) gives products undesirable properties. In addition, the suwari thus treated undergoes deterioration relating to color, especially the loss of whiteness. Therefore, the above method has not been commercially practiced, where whiteness affects the value of the meat, such as surimi made from pollack.
Also under a Japanese Patent (Toku Kai Sho No. 48-96750), it was proposed that an aqueous solution formed of a weak acid and a base be used instead of phosphates for the same purpose.
The second-mentioned method above is useful to give frozen surimi a good elasticity (a property called "ashi"). However, the fish meat processed by this method cannot be kept for long periods under refrigeration. Within this method it is advantageous to use tertiary calcium phosphate instead of polyphosphate, therefore the second-mentioned method does not reduce intake of phosphates.
In previous attempts to produce frozen surimi containing no/added phosphates, there has been no disclosure of a process to produce surimi which can be well preserved for a long period and is excellent in whiteness, water holding capacity, and good elasticity (suwari) after thawing. Prior to this invention, surimi based products, such as "kamaboko" made of conventional frozen surimi containing no phosphate, have lacked good whiteness and good elasticity.